1. Field of the Invention
The present invention relates to audio signal phone connectors, and in particular to such a connector providing a means for establishing an automatic grounded termination for the connector upon removal of the connector from an external jack. Accordingly, the general objects of the invention are to provide novel systems, methods, and apparatus of such character.
2. Description of the Related Art
The present invention is an improvement in an electrical connecting device commonly known as a “phone plug” which terminates an electrical cable and permits the cable to be readily connected and disconnected to electrical apparatus. In addition to its many other applications, the phone plug has become the standard device by which electrically amplified musical instruments are connected to their amplifiers. One of the characteristics of the phone plug that has elevated it to a standard piece of equipment for an electrical cable, is the elegant simplicity of its design. The phone plug, which has no moving parts, is sturdy and sure in performing its function permitting it to be connected and disconnected countless times without failure. The mechanical and electrical features of conventional phone connectors and jacks are well known in the art and have become standard, universally used components in the field of audio electronics.
What is also universal, however, is the highly undesirable noise that occurs when a phone plug is connected or disconnected from an instrument while the instrument's amplifier is on. Under those circumstances, it is virtually impossible to either insert or withdraw the phone plug from its jack without the tip from contacting some signal generating element, whether it be part of the jack, the person handling the equipment, or some other nearby object. When the tip makes such contact, the result is an annoying and potentially dangerous sound emanating from the speakers being driven by the amplifier to which the cable is connected. This is an annoying and unwanted noise and can be quite loud, especially for a performing musician in front of an audience.
To avoid this problem in the past, musicians had to either unplug the end of the cable that is inserted into the amplifier, or turn the amplifier volume down so that the cable could be inserted into the instrument quietly. In both cases, the musician had to take an extra step to avoid the unwanted noise. In some cases, the amplifier can be a considerable distance from the front of the stage so it can be inconvenient to do this. A professional musician might need to change instruments several times during a performance thereby compounding the problem.
These deficiencies have led to the development of audio connectors having ground switches integrated into the connector itself. These products attempt to solve this problem, however, they have been unsatisfactory as either too complicated, too costly, too unreliable, or some combination thereof. One such self-muting connector has been commercialized by Deltron. The Deltron device employs a pair of coaxial ground sleeves arranged such that one externally spring-biased sleeve may slide longitudinally relative to the other to thereby permit selective grounding based on insertion and/or removal of the connector. In practice however, the Deltron design exerts a longitudinal spring force such that it may at least partially eject the phone connector from the socket. In particular, some jack sockets have weak tip springs and are therefore not capable of holding the plug in place. If so, the plug can be ejected sufficiently to so that the signal is lost intermittently or entirely. For a performing musician, this presents a significant reliability issue. It is not desirable to be part way through a song or a solo when the signal disappears.
A second commercially available design is available from a company called Planet Waves who offers a phone connector with a manually operated switch on the side of the phone connector body. This allows the musician to manually switch the signal off before unplugging the jack from the socket. The problem with this solution however is that it still presents the musician with an extra action that needs to be performed, usually under pressure. Additionally, it is difficult to see if the switch is on or off, so the musician might not get any sound from his amplifier and/or may not deduce that it is caused by the switch being engaged in the off position.
A third connector design that solves some of the above noted problems is taught by U.S. Pat. No. 5,466,167 to Scherer. The self-muting device of the '167 patent offers the benefits that it (1) offers automatic switching operation; and (2) does not apply a longitudinal force that may tend to eject the connector from a complementary jack socket. The device taught by the '167 patent, however, is still less than optimal for a number of reasons. First, the design still involves a modest level of expense and complexity to manufacture. This aspect is critical because of the high-volume and marginally profitable nature of such devices. Second, the device of the '167 patent introduces reliability concerns that tends to undermine one of the most valuable characteristics of conventional phone connectors: astounding reliability over an extended period of time and repeated usage.
For these reasons alone, these prior art devices, as well as others of the same general description, have still not enjoyed any significant commercial success after many years.
There is, accordingly, a need in the art for improved methods, systems and apparatus to eliminate the effects of spurious extraneous signals, undesired signal emissions and signal reflections on the circuitry connected to the phone connector. In particular, such methods and apparatus should provide a simple and inexpensive connector which can be automatically muted whenever it is disconnected from an external jack socket. Such methods, systems and apparatus will ideally offer users/purchasers an optimal combination of (1) simplicity; (2) reliability; (3) economy; and (4) versatility.